It is well known to distribute television program signals from a central location to subscriber locations via coaxial cable distribution systems. Whilst such systems have long been used for broadcast television program signals, i.e. signals which are available to all subscribers without payment of further fees, they must be supplemented or modified to accommodate newer video signal services, such as pay-per-channel (PPC) and pay-per-view (PPV) television program signals. In addition, such systems have a limited capacity, i.e. a limited number of program channels which can be carried, because all of the channels available to all of the subscribers must be broadcast simultaneously.
With PPC signals, commonly the signal is scrambled at the central location and, for a payment of a fee for the channel, the subscriber is provided with a descrambler for use at his location to return the signal to its normal, receivable, form. Such procedures have led to the existence of unauthorized descramblers enabling subscribers to receive programs without payment of the fee for the channel, and to the theft of authorized scramblers.
With PPV television program signals, similar or more complex scrambling procedures may be used, but there is an additional requirement for the subscriber to communicate to the central location his desire to receive, and his agreement to pay for, a particular program. This communication requires an upstream communications path from the subscriber location to the central location, in addition to the downstream communications path via which the television program signals are distributed. Such an upstream communications path is not conveniently provided by cable distribution systems, and generally must be provided via other equipment, such as the telephone system or other equipment at the subscriber's location. Furthermore, the communications and addressable decoders which are involved with PPV signals lead to undesirable congestion in broadcast networks.
In each of these instances, the fact that the television program signals are distributed in a general manner from the central location to all of the subscriber locations means that control of the signals by their distributor is lost, and the signals are exposed to theft with consequent loss of revenues.
With increasing bandwidths available on communications paths which have conventionally served for only telephone communications, for example through the use of optical fiber communications paths and especially the extension of such paths from a central location to subscriber locations, it is increasingly becoming possible to use such communications paths not only for telephone communications but also for other services, such as video signal distribution, enabling the provision of cable distribution systems to subscriber locations to be dispensed with.
Accordingly an object of this invention is to provide an improved signal distribution system for distributing video signals.